The cell wall polysaccharide of Trichosporon beigelii that cross-reacts with the capsular glucuronoxylomannan of Cryptococcus neoformans was further characterized immunologically. Previously, among other epitopes, we had established the presence of glucuronic acid and O-acetyl epitopes on the T. beigelii polysaccharide by NMR and chemical means. We have confirmed the identity of T. beigelii polysaccharide with the glucuronoxylomannan of C. neoformans with reference to these two important epitopes by using two monoclonal antibodies to the glucuronyl and O-acetyl epitopes of the cryptococcal glucuronoxylomannan (a gift from Dr. T. Kozel, University of Nevada, Las Vegas). Both the polysaccharides showed an identical pattern of precipitation with the two monoclonal antibodies. In C. neoformans, both glucuronyl and O-acetyl epitopes are closely associated with virulence, immunogenicity and biological activity. Our previous demonstration of a good correlation between the amount of polysaccharide present in deep-seated isolates and the degree of resistance to phagocytosis along with the current results suggest the possible role of T. beigelii polysaccharide in pathogenesis of septicemia and other deep-seated infections.